Project Summary: The goal of this proposal is to develop high throughput cell-based assays for the identification of small molecule inhibitors of mucin-type O-linked glycans. Mucin-type O-linked glycan structures play critical roles in inflammation and tumor metastasis; however, no small molecule, non carbohydrate inhibitors have been identified. The cell-based assays described herein have the ability to discover inhibitors of any biosynthetic enzyme required for the synthesis of mucin-type O linked glycans. Inhibitors of O-linked glycan biosynthetic enzymes would be powerful research tools to probe the biological roles of this class of carbohydrates. Furthermore, inhibitors would be starting points to develop therapeutics for treating cancer, inflammatory diseases, and infection caused by influenza and Helicobacter pylori. Relevance: Carbohydrates play essential roles in many human diseases; however, drugs targeting this class of molecules are generally lacking. This proposal aims to solve this problem by developing a high throughput screening system to identify small molecule inhibitors of a specific class of cell surface carbohydrates known as mucin-type O-linked glycans. Small molecules identified by the methods proposed here would have value as research tools and as the starting point to develop a new class of Pharmaceuticals for treating cancer and infectious diseases.